My data are 3 sets of X and Y, each of them got 49 pairs
ChartData is a variant (49,6), that are assigned as per the following:

Chartdata(x,1)=x values of first set
Chartdata(x,2)=y values of first set
Chartdata(x,3)=x values of second set
Chartdata(x,4)=y values of second set
Chartdata(x,5)=x values of third set
ChartData(x,6)=y values of third set

I am looking at the minimum and maximum values that Y can take (these are MinY and MaxY).

The problem is that the chart shows some values being 0, but looking at the vector they are not ...